xu 



So soon as the twist from one end is fully resisted by 

 that from the other, the line of counter action across the 

 thickness of the rod has that end of it which the active 

 tnm directly affects drawn to one side. 



The drawing to one side of this end fixes the other end 

 of the cross line which is affected by the counter-twist so 

 that this latter cannot work directly upon it from the 

 originating point. 



This fixed displacement of one end of the cross line 

 causes the w^orking of the second twist to be diffused 

 through the rod, and thus the ensuing spring may have for 

 its points of appui a point at the centre of the rod, and a 

 point of rest on the ground at one end of the rod, and on 

 the same side as that at the centre, instead of having both 

 points at the centre and on opposite sides. 



It is thus that a movement in j)rogression or retrogres- 

 sion may be obtained, instead of a spring in two directions, 

 from the centre of the rod. 



The fundamental action of locomotion is, then, the forma- 

 tion and discharge of two counter-turns in an elastic rod ; 

 the turn discharged giving the spring, and the other, after 

 controlling this spring, presenting through the counter- 

 turn it has developed at the cross line, the shape for the 

 alternate of the first, which again receives a counter-turn, 

 and so on. 



The displacement to a greater or less degree of the end of 

 the cross line affected by the second turn of one set of 

 diagonal counter-turns becoming permanent, and thus in- 

 terfering with the action of the alternate set is the cause of 

 the general deformity spoken of above. The reduction of this 

 displacement by strengthening those muscles which work 

 the alternate winding lines, and the giving position to the 

 alternate and opposing cross line, is its cure. 



The body of the snake presents an elastic compound rod, 

 which moves by forming, discharging, and, after each 



